1. Field of the Invention
The present invention relates to a lapping apparatus to lap a work piece. More particularly, it relates to a lapping apparatus to lap a work piece with high accuracy.
For example, after forming a magnetic head thin film, the magnetic head thin film is lapped on the process of manufacturing a magnetic head. Heights of a magnetic resistance layer and a gap of the magnetic head thin film of the magnetic head are made to have a certain constant by lapping on the manufacturing process of the magnetic head.
For the heights of the magnetic resistance layer and the gap, sub-micron order of accuracy is required. Therefore, it is necessary to lap work pieces or magnetic thin films with high accuracy.
2. Description of the Related Art
FIGS. 23A and 23B are explanatory diagrams of a composite type magnetic head.
As shown in FIG. 23A, the composite type magnetic head includes a magnetic resistance element 82 formed on a base plate 81 and a writing element 85. The magnetic resistance element 82 is formed of a magnetic resistance film 83 and a pair of conducting films 84. A resistance value of the magnetic resistance element 82 is varied by an external magnetic field. The magnetic resistance element 82 has a function to read out an electric current having a value according to magnetic field strength of a track 90 on a magnetic disk.
As the magnetic resistance element 82 is an element for reading out the current, it is required to provide a different element 85 for writing. The writing element 85 includes an inductive head. The inductive head is comprised of a lower magnetic pole 86, an upper magnetic pole 88 faced to the lower magnetic pole 86 with a certain gap, and a coil 87 provided between the lower and upper magnetic poles 86 and 88 to magnetically excite them. A non-magnetic insulating layer 89 is provided around the coil 87.
In such the composite type magnetic head, it is required to have a constant resistance value of the magnetic resistance film 83 in the magnetic resistance element 82 for each magnetic head. However, it is difficult to make the resistance value be constant or uniform on the process of manufacturing the thin film for the magnetic head. Therefore, after forming the thin film of the magnetic head, a height (width) h of the magnetic resistance film 83 is adjusted so that a resistance value may be uniformed.
FIGS. 24A, 24B, 25A, 25B, 25C and 25D are diagrams explaining the process of manufacturing the composite type magnetic head.
As shown in FIG. 24A, a plurality of composite type magnetic heads are formed on a semiconductor wafer 100 by a thin film technique. Next, as shown in FIG. 24B, the wafer 100 is cut into strips to make a plurality of row bars 101. A row bar 101 includes a plurality of the magnetic heads 102 arranged in one row. Resistance elements 102a are provided on the left and right ends, and at the center of the row bar 101 for monitoring the process of the manufacturing.
As described above, the height of the magnetic resistance film 83 for the magnetic head 102 is lapped to be constant or uniform. However, the row bar 101 is extremely thin, for example, about 0.3 mm. It is, therefore, difficult to mount the row bar 101 directly to a lapping jig, and as shown in FIG. 24C, the row bar 101 is bonded to a mounting tool or base 103 with heat dissoluble wax.
Then, as shown in FIG. 25A, the row bar 101, which is bonded to the mounting base 103, is placed on a lapping plate 104 for lapping the row bar 101. As known in Japanese Unexamined patent application published No. 2-124262 (U.S. Pat. No. 5,023,991) or Japanese Unexamined patent application published No. 5-123960, the resistance value of the resistance element 102a for monitoring is always measured while lapping the row bar 101. Then, it can be detected whether or not the magnetic resistance film of the magnetic head 102 has become a targeted height.
When it is detected by the measurement of the resistance value that the magnetic resistance film has been lapped to the targeted height, the lapping processing is stopped. After that, a slider can be formed on a bottom surface 101-1 of the row bar 101, as shown in FIG. 25B.
The row bar 101 is further cut into a plurality of magnetic heads 102, as the row bar 101 is mounted on the mounting base 103 as shown in FIG. 25C. Each magnetic head 102 is taken out from the mounting base 103 by heating and melting the heat dissoluble wax, as shown in FIG. 25D.
In this way, a row bar 101 including a plurality of the magnetic heads 102 is prepared, and lap processing is performed for the row bar 101. Therefore, the magnetic resistance film on the plurality of magnetic heads 102 can be lapped by one step.
FIG. 26 is an explanatory diagram of a conventional lapping apparatus, and FIG. 27 is a diagram explaining a supporting mechanism for work piece.
The lapping apparatus has a rotary lapping plate 104, as shown in FIG. 26. A supporting block 105 has three pads 105a contacting to the lapping plate 104. The pads 105a smoothly spread slurry (abrasive liquid) on the lapping plate 104 and fill the slurry into the lapping plate 104. The pads 105a, further, may soften pressure of the supporting block 105 to the surface of the lapping plate 104.
The supporting block 105 is swung on the lapping plate 104 by a swing mechanism 106. The supporting block 105 supports the mounting base 103. Therefore, the row bar 101, which is bonded to the mounting base 103, is lapped by the rotation of the lapping plate 104 and the swing of the block 105.
As shown in FIG. 27A, the mounting base 103 was directly mounted to the supporting block 105 in the conventional apparatus. Therefore, the block 105 follows the lapping plate 104. Thereby, the work piece 101 is lapped.
As explained above, the mounting base 103 was directly mounted to the supporting block 105 following to the lapping plate 104 in the conventional apparatus, and therefore, accuracy (the degree of a right angle) between the following surface of the block 105 and the mounting surface of the block 105 should be required. If the following surface of the block 105 is not exact at a right angle to the mounting surface of the block 105, as shown in FIG. 27B, the row bar 101 bounded to the mounting base 103 may be lapped as inclined to the lapping plate 104. Therefore, the row bar 101 which is bonded to the mounting base 103 is diagonally lapped by the lapping plate 104.
When accuracy is required in sub-microns for a work piece such as the row bar 101, it is difficult to uniformly lap the work piece. It has taken too much time to accurately obtain the right angle between the surfaces of the block 105.
In addition, it has been extremely difficult to keep the accuracy between the following processing surface of the block 105 and the mounting surface, as the surfaces on the block 105 are wearing according to frequencies of the use.